We present an analysis of 15 Type Ia supernovae (SNe Ia) at redshift (9 at ) recently discovered in the CANDELS and CLASH Multi-Cycle Treasury programs using WFC3 on the Hubble Space Telescope. We ...combine these SNe Ia with a new compilation of ∼1050 SNe Ia, jointly calibrated and corrected for simulated survey biases to produce accurate distance measurements. We present unbiased constraints on the expansion rate at six redshifts in the range based only on this combined SN Ia sample. The added leverage of our new sample at leads to a factor of ∼3 improvement in the determination of the expansion rate at z = 1.5, reducing its uncertainty to ∼20%, a measurement of . We then demonstrate that these six derived expansion rate measurements alone provide a nearly identical characterization of dark energy as the full SN sample, making them an efficient compression of the SN Ia data. The new sample of SNe Ia at usefully distinguishes between alternative cosmological models and unmodeled evolution of the SN Ia distance indicators, placing empirical limits on the latter. Finally, employing a realistic simulation of a potential Wide-Field Infrared Survey Telescope SN survey observing strategy, we forecast optimistic future constraints on the expansion rate from SNe Ia.
ABSTRACT We use rest-frame optical and near-infrared (NIR) observations of 42 Type Ia supernovae (SNe Ia) from the Carnegie Supernova Project at low-z and 37 from the RAISIN (SNIA in the IR) Survey ...at high-z to investigate correlations between SN Ia host galaxy dust, host mass, and redshift. This is the first time the SN Ia host galaxy dust extinction law at high-z has been estimated using combined optical and rest-frame NIR data (YJ band). We use the BayeSN hierarchical model to leverage the data’s wide rest-frame wavelength range (extending to ∼1.0–1.2 μm for the RAISIN sample at 0.2 ≲ z ≲ 0.6). By contrasting the RAISIN and Carnegie Supernova Project (CSP) data, we constrain the population distributions of the host dust RV parameter for both redshift ranges. We place a limit on the difference in population mean RV between RAISIN and CSP of −1.16 < Δμ(RV) < 1.38 with 95 per cent posterior probability. For RAISIN we estimate μ(RV) = 2.58 ± 0.57, and constrain the population standard deviation to σ(RV) < 0.90 2.42 at the 68 95 per cent level. Given that we are only able to constrain the size of the low- to high-z shift in μ(RV) to ≲1.4 – which could still propagate to a substantial bias in the equation-of-state parameter w – these and other recent results motivate continued effort to obtain rest-frame NIR data at low- and high-redshifts (e.g. using the Roman Space Telescope).
We report observations of two nearby Type Ia supernovae (SNe Ia) for which observations of Cepheid variables in the host galaxies have been obtained with the Hubble Space Telescope: SN 1994ae in NGC ...3370 and SN 1998aq in NGC 3982. For NCG 3370, we used the Advanced Camera for Surveys to observe 64 Cepheids that yield a distance of 29 Mpc, the farthest direct measurement of Cepheids. We have measured emission lines from H II regions in both host galaxies that provide metallicity-dependent corrections to their period-luminosity relations. These two SNe Ia double the sample of "ideal" luminosity calibrators: objects with well-observed and well-calibrated light curves of typical shape and with low reddening. By comparing them to all similarly well-measured SNe Ia in the Hubble flow, we find that H sub(0) = 73 c 4 (statistical) c 5 (systematic) km s super(-1) Mpc super(-1). A detailed analysis demonstrates that most of the past disagreement over the value of H sub(0) as determined from SNe Ia is abated by the replacement of past, problematic data by more accurate and precise, modern data.
We present UBVRIJHK photometry and optical spectroscopy of the so-called peculiar Type Ia supernova 1999by in NGC 2841. The observations began 1 week before visual maximum light, which is well ...defined by daily observations. The light curves and spectra are similar to those of the prototypical subluminous event SN 1991bg. We find that maximum light in B occurred on 1999 May 10.3 UT (JD 2,451,308.8 plus or minus 0.3) with B = 13.66 plus or minus 0.02 and a color of B sub(max) - V sub(max) = 0.51 plus or minus 0.03. The late-time color implies minimal dust extinction from the host galaxy. Our photometry, when combined with the recent Cepheid distance to NGC 2841, gives a peak absolute magnitude of M sub(B) = -17.15 plus or minus 0.23, making SN 1999by one of the least luminous Type Ia events ever observed. We estimate a decline rate parameter of Delta m sub(15)(B) = 1.90 mag, versus 1.93 for SN 1991bg, for which 1.10 is typical for so-called normal events. We compare SN 1999by with other subluminous events and find that the B sub(max) - V sub(max) color correlates strongly with the decline rate and may be a more sensitive indicator of luminosity than the fading rate for these objects. We find a good correlation between luminosity and the depth of the spectral feature at 580 nm, which had been attributed solely to Si II. We show that in cooler photospheres the 580 nm feature is dominated by Ti II, which provides a simple physical explanation for the correlation. Using only subluminous Type Ia supernovae, we derive a Hubble parameter of H sub(0) = 75 super(+) sub(-) super(1) sub(1) super(2) sub(1) km s super(-1) Mpc super(-1), consistent with values found from brighter events.
We study the effect of environment on the properties of Type Ia supernovae by analyzing the integrated spectra of 57 local Type Ia supernova host galaxies. We deduce from the spectra the metallicity, ...current star formation rate, and star formation history of the host and compare these to the supernova decline rates. Additionally, we compare the host properties to the difference between the derived supernova distance and the distance determined from the best-fit Hubble law. From this we investigate possible uncorrected systematic effects inherent in the calibration of Type Ia supernova luminosities using light-curve fitting techniques. Our results indicate a statistically insignificant correlation in the direction of higher metallicity spiral galaxies hosting fainter Type Ia supernovae. However, we present qualitative evidence suggesting that progenitor age is more likely to be the source of variability in supernova peak luminosities than is metallicity. We do not find a correlation between the supernova decline rate and host galaxy absolute B magnitude, nor do we find evidence of a significant relationship between decline rate and current host galaxy star formation rate. A tenuous correlation is observed between the supernova Hubble residuals and host galaxy metallicities. Further host galaxy observations will be needed to refine the significance of this result. Finally, we characterize the environmental property distributions for Type Ia supernova host galaxies through a comparison with two larger, more general galaxy distributions using Kolmogorov-Smirnov tests. The results show the host galaxy metallicity distribution to be similar to the metallicity distributions of the galaxies of the NFGS and SDSS. Significant differences are observed between the SN Ia distributions of absolute B magnitude and star formation histories and the corresponding distributions of galaxies in the NFGS and SDSS. Among these is an abrupt upper limit observed in the distribution of star formation histories of the host galaxy sample, suggesting a Type Ia supernovae characteristic delay time lower limit of approximately 2.0 Gyr. Other distribution discrepancies are investigated and the effects on the supernova properties are discussed.
One of the major differences between various explosion scenarios of Type Ia supernovae (SNe Ia) is the remaining amount of unburned (C+O) material and its velocity distribution within the expanding ...ejecta. While oxygen absorption features are not uncommon in the spectra of SNe Ia before maximum light, the presence of strong carbon absorption has been reported only in a minority of objects, typically during the pre-maximum phase. The reported low frequency of carbon detections may be due to low signal-to-noise data, low abundance of unburned material, line blending between C II Delta *l6580 and Si II Delta *l6355, ejecta temperature differences, asymmetrical distribution effects, or a combination of these. However, a survey of published pre-maximum spectra reveals that more SNe Ia than previously thought may exhibit C II Delta *l6580 absorption features and relics of line blending near ~6300 A. Here we present new SN Ia observations where spectroscopic signatures of C II Delta *l6580 are detected and investigate the presence of C II Delta *l6580 in the optical spectra of 19 SNe Ia using the parameterized spectrum synthesis code, SYNOW. Most of the objects in our sample that exhibit C II Delta *l6580 absorption features are of the low-velocity gradient subtype. Our study indicates that the morphology of carbon-rich regions is consistent with either a spherical distribution or a hemispheric asymmetry, supporting the recent idea that SN Ia diversity may be a result of off-center ignition coupled with observer line-of-sight effects.
We present the most sensitive ultraviolet observations of Supernova 1987A to date. Imaging spectroscopy from the Hubble Space Telescope-Cosmic Origins Spectrograph shows many narrow ( Delta *Dv ~ 300 ...km s--1) emission lines from the circumstellar ring, broad ( Delta *Dv ~ 10-20 X 103 km s--1) emission lines from the reverse shock, and ultraviolet continuum emission. The high signal-to-noise ratio (>40 per resolution element) broad Ly Delta *a emission is excited by soft X-ray and EUV heating of mostly neutral gas in the circumstellar ring and outer supernova debris. The ultraviolet continuum at Delta *l > 1350 A can be explained by H I two-photon (2s 2 S 1/2-1s 2 S 1/2) emission from the same region. We confirm our earlier, tentative detection of N V Delta *l1240 emission from the reverse shock and present the first detections of broad He II Delta *l1640, C IV Delta *l1550, and N IV Delta *l1486 emission lines from the reverse shock. The helium abundance in the high-velocity material is He/H = 0.14 ? 0.06. The N V/H Delta *a line ratio requires partial ion-electron equilibration (Te /Tp 0.14-0.35). We find that the N/C abundance ratio in the gas crossing the reverse shock is significantly higher than that in the circumstellar ring, a result that may be attributed to chemical stratification in the outer envelope of the supernova progenitor. The N/C abundance may have been stratified prior to the ring expulsion, or this result may indicate continued CNO processing in the progenitor subsequent to the expulsion of the circumstellar ring.
Highlights • Multi-joint coordination in one-leg stance was examined by a frequency domain PCA. • Two strategies were observed implying individual differences in postural control. • Visual ...information influences the prevalence of the two postural strategies.
We present spectral and photometric observations of 10 Type Ia supernovae in the redshift range z = 0.16-0.62. The luminosity distances of these objects are determined by methods that employ ...relations between SN Ia luminosity and light curve shape. This expanded set of 16 high-redshift supernovae and a set of 34 nearby supernovae are used to place constraints on the following cosmological parameters: the Hubble constant (H0), the mass density (M), the cosmological constant, the deceleration parameter (q0), and the dynamical age of the universe (t0). The distances of the high-redshift SNe Ia are, on average, 10-15 percent farther than expected in a low mass density universe without a cosmological constant. Different light curve fitting methods, SN Ia subsamples, and prior constraints unanimously favor eternally expanding models with positive cosmological constant and a current acceleration of the expansion. With no prior constraint on mass density other than Omega(M) = 0 or greater, the spectroscopically confirmed SNe Ia are statistically consistent with q0 less than 0 at the 2.8 sigma and 3.9 sigma confidence levels, and with Omega(Lambda) greater than at the 3.0 sigma and 4.0 sigma confidence levels, for two different fitting methods, respectively. A universe closed by ordinary matter is formally ruled out at the 7 to 8 sigma confidence level for the two different fitting methods. We estimate the dynamical age of the universe to be 14.2 +/- 1.7 Gyr. (Author)
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